1. Field of the Invention
This invention relates generally to electrical connectors, and particularly to an electrical communications connector arranged to compensate for crosstalk among conductive signal paths carried through the connector.
2. Discussion of the Known Art
There is a need for a durable, high frequency communications connector that compensates for (i.e., cancels or reduces) crosstalk among signal paths carried by the connector. As broadly defined herein, crosstalk occurs when signals conducted over a first signal path, e.g., a pair of terminal contact wires within a connector, are partly transferred by inductive or capacitive coupling into a second, adjacent signal path (e.g., another pair of terminal contact wires) within the connector. The transferred signals become "crosstalk" in the second signal path, and they act to degrade any signals that are being routed through the second path.
For example, an industry type RJ-45 communications connector has four pairs of terminal wires defining four different signal paths. In typical RJ-45 plug and jack connectors, all four pairs of terminal wires extend closely parallel to one another over the lengths of the connector bodies. Thus, crosstalk may be induced between and among different pairs of terminal wires within the typical RJ-45 plug and jack connectors, particularly when the connectors are mated to one another. The induced crosstalk also becomes stronger as signal frequencies or data rates increase.
Applicable industry standards for rating the extent to which communication connectors exhibit crosstalk, do so in terms of so-called near end crosstalk or "NEXT". Moreover, such ratings are typically specified for a mated pair of connectors, e.g., a type RJ-45 plug and jack combination, using the input terminals of the plug connector as a reference plane.
U.S. Pat. No. 5,186,647 to Denkmann et al. (Feb. 16, 1993), which is assigned to the assignee of the present invention and application, discloses an electrical connector for conducting high frequency signals. The connector has a pair of metallic lead frames mounted flush with a dielectric spring block, with connector terminals formed at opposite ends of the lead frames. The lead frames themselves include flat elongated conductors each of which includes a spring terminal contact wire at one end for contacting a corresponding terminal wire of a mating connector, and an insulation displacing connector terminal at the other end for connection with an outside insulated wire lead. The lead frames are placed over one another on the spring block, and three conductors of one lead frame have cross-over sections configured to overlap corresponding cross-over sections formed in three conductors of the other lead frame. All relevant portions of the mentioned '647 patent are incorporated by reference herein. U.S. Pat. No. 5,580,270 (Dec. 3, 1996) also discloses an electrical plug connector having crossed pairs of contact strips.
It is also known to provide crosstalk compensating circuitry on or within layers of a printed wire board, to which spring terminal contact wires of a communication jack are connected within the jack housing. See U.S. patent application Ser. No. 08/923,741 filed Sep. 29, 1997, and assigned to the assignee of the present invention and application. All relevant portions of the '741 application are incorporated by reference herein.
Communication links using unshielded twisted pairs of copper wire are now expected to support reliably data rates up to not only 100 MHz, or industry standard "Category 5" performance; but up to as much as 250 MHz or proposed "Category 6" performance levels. A so-called "HighBand" jack from Krone AG is claimed to exceed Category 5 requirements. The jack includes a printed wire board, and four pairs of terminal contact wires extending normally to the board surface in a non-coplanar configuration. A center pair of the contact wires cross over one another.
Thus, there is a need for a communications connector whose crosstalk characteristics approach Category 6 levels. Likewise, a jack connector which, when mated with a typical type RJ-45 plug connector, compensates for crosstalk in such a way that the mated connectors meet or surpass Category 6 performance, would be highly desirable.